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<title>Problem 2134. -- 单选错位 -- 衡阳八中OJ离线版-2012-02-29</title><center><h2>2134: 单选错位</h2><span class=green>Time Limit: </span>10 Sec&nbsp;&nbsp;<span class=green>Memory Limit: </span>259 MB<br><span class=green>Submit: </span>118&nbsp;&nbsp;<span class=green>Solved: </span>82<br>[<a href='submitpage.php?id=2134'>Submit</a>][<a href='problemstatus.php?id=2134'>Status</a>][<a href='bbs.php?id=2134'>Discuss</a>]</center><h2>Description</h2><div class=content><p><img border="0" alt="" src="images/2134.jpg" /></p></div><h2>Input</h2><div class=content><p>n很大，为了避免读入耗时太多，输入文件只有5个整数参数n, A, B, C, a1，由上交的程序产生数列a。下面给出pascal/C/C++的读入语句和产生序列的语句（默认从标准输入读入）： // for pascal readln(n,A,B,C,q[1]); for i:=2 to n do q[i] := (int64(q[i-1]) * A + B) mod 100000001; for i:=1 to n do q[i] := q[i] mod C + 1; // for C/C++ scanf(&quot;%d%d%d%d%d&quot;,&amp;n,&amp;A,&amp;B,&amp;C,a+1); for (int i=2;i&lt;=n;i++) a[i] = ((long long)a[i-1] * A + B) % 100000001; for (int i=1;i&lt;=n;i++) a[i] = a[i] % C + 1; 选手可以通过以上的程序语句得到n和数列a（a的元素类型是32位整数），n和a的含义见题目描述。</p></div><h2>Output</h2><div class=content><p>输出一个实数，表示gx期望做对的题目个数，保留三位小数。</p></div><h2>Sample Input</h2>
			<div class=content><span class=sampledata>3 2 0 4 1<br />
</span></div><h2>Sample Output</h2>
			<div class=content><span class=sampledata>1.167<br />
【样例说明】<br />
a[] = {2,3,1}<br />
正确答案	gx的答案	做对题目	出现概率<br />
{1,1,1}	{1,1,1}	3	1/6<br />
{1,2,1}	{1,1,2}	1	1/6<br />
{1,3,1}	{1,1,3}	1	1/6<br />
{2,1,1}	{1,2,1}	1	1/6<br />
{2,2,1}	{1,2,2}	1	1/6<br />
{2,3,1}	{1,2,3}	0	1/6<br />
共有6种情况，每种情况出现的概率是1/6，gx期望做对(3+1+1+1+1+0)/6 = 7/6题。（相比之下，lc随机就能期望做对11/6题）<br />
【数据范围】<br />
对于100%的数据 2≤n≤10000000, 0≤A,B,C,a1≤100000000<br />
</span></div><h2>HINT</h2>
			<div class=content><p></p></div><h2>Source</h2>
			<div class=content><p><a href='problemset.html?search=By 高欣'>By 高欣</a></p></div><center>[<a href='submitpage.php?id=2134'>Submit</a>][<a href='problemstatus.php?id=2134'>Status</a>][<a href='bbs.php?id=2134'>Discuss</a>]</center>﻿<br>

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